A trend in data communications is to increase the use of optical fiber as a media. In an optical fiber communications system, voice, video, or data are converted to a coded pulse stream of light. This pulse. stream is carried by optical fibers to a receiving or regenerating station. At the final receiving station, the light pulses are converted into the form of the original information.
A big advantage of an optical communication system is its tremendous information carrying capability. By multiplexing different channels, a single optical fiber can carry thousands of channels at the same time.
The primary parameters used for multiplexing optical channels are wavelengths, time, frequency, phase, and space. Wavelength division multiplexing (WDM) involves the use of different wavelengths, and is currently in wide use.